Method for managing the regeneration of a diesel particulate filter (dpf) in a diesel engine system

ABSTRACT

A method is provided for managing the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system. The engine having an intake and an exhaust line and being configured to after-inject or post-inject quantities of fuel into a combustion chamber for raising the temperature of the engine exhaust gas. The engine including in the exhaust line, but not limited to, a Diesel Particulate Filter (DPF). The method including, but not limited to identifying a faulty condition of the engine system and, in case that such faulty condition is not critical, measuring the intake air charge and, in case such intake air charge is acceptable, and performing a regeneration process for said Diesel Particulate Filter (DPF).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to British Patent Application No. 1001446.2, filed Jan. 29, 2010, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates to a method for managing the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system.

BACKGROUND

Diesel engines, in order to satisfy tight emission legislation, are typically equipped with a Diesel Particulate Filter (DPF). This is an aftertreatment device, located in the exhaust line, which is able to capture particulate matter such as soot produced by combustion. Different location are possible for the DPF, according to the exhaust line/system architecture: i.e. a close-coupled DPF (CC), or an underfloor DPF (UF).

Powertrain engine management systems (ECU) typically include DPF specific control strategies to perform the following tasks, namely: determination of DPF filling level performance of the automatic procedure to empty-out the DPF once a certain filling level has been detected, this latter procedure being the so-called DPF regeneration process The DPF regeneration process is carried out during normal driving operation, no service or maintenance intervention being necessary.

The DPF regeneration process is a controlled combustion of the soot, internal to the DPF, ignited by means of a temperature increase of the exhaust gases flowing throughout the DPF. For example, this temperature increase, up to approximately 630° C., has to be kept for a certain time (typically about 10 minutes) in all possible driving conditions, namely city driving, highway driving, and so on.

Exhaust gas temperature increase is obtained with a dedicated combustion mode, whereby mainly Fuel system and Air system controls are involved, during the regeneration process, by means of which the system gets a first temperature increase due to fuel combustion inside combustion chamber and a second temperature increase due to fuel oxydation inside the catalyst present in the exhaust line. With the DPF regeneration process dedicated combustion mode, the typical injection pattern (fuel system) and air system actuators regulation (EGR, throttle, turbo charger) are changed to support the regeneration process itself. To get the first temperature increase, the dedicated combustion mode performs a so called After-Injection which is a late fuel injection, namely an injection that occurs after top dead center (TDC); this additional fuel injection burns inside the combustion chamber.

To obtain the second temperature increase, the dedicated combustion mode performs at least a so-called Post-Injection (typically more than one) which is also a late fuel injection, an in particular occurs later than the After-Injection. This additional fuel injection does not burn inside the combustion chamber, but reaches the diesel oxidation catalyst (DOC) in the exhaust line upstream the DPF where it oxidises releasing heat.

Along with dedicated fuel injection management, a key role is played also by a dedicated intake air management: various parameters such Exhaust Gas Recirculation (EGR), throttle valve position, turbine control, swirl control, etc. are managed according to engine status to provide the necessary air charge to support DPF regeneration (RGN) specific combustion mode. In particular, both the necessary oxygen content inside the combustion chamber as well as at exhaust pipe is provided.

Current strategies for regeneration process are able to achieve the necessary target temperature for the exhaust gases to regenerate the DPF in most of the driving conditions typically recognizable in terms of engine fuelling or Brake Mean Effective Pressure (BMEP), engine speed, and vehicle speed. Current production systems (mainly Euro 4 systems) allow DPF regeneration only if no faults on the system are present so to always perform the process in optimal conditions. Field issues revealed that this approach, joint with a mandatory vehicle equipment with DPF due to impending emission legislation, is causing several not needed service intervention for DPF forced regeneration, and lots of customer complaints due to walk home failure. One of the main reasons for these issues is that the inhibition of the DPF regeneration any case of any faulty condition of the engine leads to DPF clogging in case of untimely service intervention; also, DPF clogging could even cause engine performance limitation.

In view of the foregoing, at least on object is to devise conditions suitable to allow a safety DPF regeneration process. Another object is to provide a method for operating the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system without using complex devices and by taking advantage from the computational capabilities of the Electronic Control Unit (ECU) of the vehicle. At least another object is to meet these goals by means of a simple, rational and inexpensive solution. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

An embodiment is provided for a method for managing the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system, the engine having an intake and an exhaust line and being configured to after-inject or post-inject quantities of fuel into a combustion chamber for raising the temperature of the engine exhaust gas, the engine comprising in said exhaust line a Diesel Particulate Filter (DPF), the method comprising the following steps: identify a faulty condition of the engine system and, in case that such faulty condition is not critical, measure the intake air charge and, in case such intake air charge is acceptable, and perform a regeneration process for said Diesel Particulate Filter (DPF). Such embodiment has the advantage of performing the regeneration process on the DPF also in case of non-critical faulty conditions of the engine system.

A further embodiment provides for a method for operating the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system in which said measurement of the intake air charge is performed measuring intake air flow rate and intake air pressure in order to determine if these parameters are inside an acceptable range for initiating the regeneration process. This embodiment has the advantage of performing a regeneration process in case of non-critical faulty conditions and only when the engine system is performing with acceptable conditions.

A still further embodiment provides for a method for operating the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system in which said the acceptable range of the intake air charge is determined as a function of engine working point. This embodiment has the advantage of performing a regeneration process in case of non-critical faulty conditions and only when the engine system is performing within acceptable conditions depending on the working point of the engine.

Another embodiment provides for a method for operating the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system in which said regeneration process is performed in a safe mode. Such embodiment has the advantage of performing a regeneration process even in case of non-critical faulty conditions using a safety regeneration strategy.

Another embodiment provides for a method in which said safety-mode regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to the temperature set-point and duration of a conventional DPF regeneration process. This embodiment has the advantage of performing a safer regeneration process even in case of non-critical faulty conditions of the engine system.

The method according to one of the embodiments can be realized in the form of a computer program comprising a program-code to carry out all the steps of the method and in the form of a computer program product comprising means for executing the computer program. The computer program product comprises, according to an embodiment, a control apparatus for an IC engine, for example the ECU of the engine, in which the program is stored so that the control apparatus defines such embodiment or embodiments in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method according to the embodiments described are carried out.

The method according to one of the embodiments can be also realized in the form of an electromagnetic signal. The signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

A still further embodiment provides an internal combustion engine specially arranged for carrying out the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing FIG. 1, which is a schematic representation illustrating a flowchart of the steps of the method in accordance with an embodiment.

DETAILED DESCRIPTION

The following detailed description of the invention is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description of the invention.

The method for managing the regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system, provides first for the identification of the presence of any faulty condition of the engine system in the check fault stage of FIG. 1. Most frequently part of the faulty conditions such identified are not major or critical faulty conditions for the engine and in particular the air system: they require of course service intervention but DPF regeneration process can be performed anyway (preferably along with safety settings as explained below). In this way DPF clogging may be avoided and hence avoid additional intervention at service, which means that there is no need for the forced DPF regeneration process at service.

A diagnostic check is performed to properly recognize whether an air system fault should drive DPF regeneration process inhibition, or if it can allow a safety DPF regeneration process. This latter safety DPF regeneration process may also be called a Recovery regeneration process having dedicated safety settings. Preferably, for safety, said regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to the temperature set-point and duration of a conventional DPF regeneration process.

As a second step of the method, in case that the faulty condition detected is not critical, the intake air charge is measured and, in case such intake air charge is acceptable, a regeneration process for said Diesel Particulate Filter (DPF) is performed. Specifically measurement of the intake air charge is performed measuring intake air flow rate (MAF) and intake air pressure (p) in order to determine if these parameters are inside an acceptable range for initiating said regeneration process. If the faulty condition is critical, no DPF regeneration is performed.

In fact in some cases too much fresh air could lead to DPF regeneration low temperature (not enough heat release), in other cases it could represent too high oxygen content in the exhaust leading to un-controlled soot combustion leading to DPF thermal stress. Preferably the determination the intake air flow rate (MAF) is performed by means of a mass air flow sensor in a inlet line of the engine and the determination the intake air pressure (p) is performed by means of a pressure sensor in the intake manifold of the engine. In this way it is possible to measure an acceptable intake air charge, in terms of intake air flow rate or in term of intake air pressure. If the intake air charge is acceptable, the DPF regeneration is allowed, preferably in a Recovery or safety mode. Preferably the acceptable range of the intake air charge is not constant but is determined as a function of engine working point. That means that, depending on engine working point, expressed in term of engine load (i.e., torque, fuelling, Brake Mean Effective Pressure (BMEP)) and engine speed, intake air charge is regulated so to properly support a DPF regeneration combustion mode according to the embodiment described.

Which and how many faulty conditions are used in the method, depends on system architecture and on specific ECU strategy applied to properly support DPF regeneration combustion mode. By faulty condition it is meant faulty conditions that may derive from the whole engine system, and in particular from engine air system. A condition is defined to be critical when it causes an excessive heating of the DPF, and thus thermal stress, during the regeneration period. More precisely, the faulty condition is regarded to be critical when it causes the temperature of the DPF to exceed a threshold value.

Examples of non-critical faults are faults connected to variable blade turbine malfunction, would be a throttle valve blocked in an intermediate position, a variable swirl actuator blocked close, a variable swirl actuator blocked in an intermediate position or any fault on turbocharger. Examples of critical faults would be an EGR valve blocked open or an EGR valve blocked in an intermediate position.

Which DPF regeneration settings are changed to perform a Recovery regeneration process depends on specific ECU strategy to perform the regeneration process: these could be, for example, temperature set-point for the regeneration and process duration. Preferably a safety-mode DPF regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to the temperature set-point and duration of a conventional DPF regeneration process.

Temperature increase for the DPF regeneration in a safety mode are reached in a conventional manner, namely performing an After-Injection and one or more Post-Injections that reach the Diesel Oxidation Catalyst (DOC) in the exhaust line upstream the DPF where it oxidises releasing heat.

The embodiments described have several important advantages and benefits. First, a reduced possibility of DPF clogging is obtained Also, the occurrence of “walk home” failures are reduced. Moreover, a reduced service intervention that implies a DPF forced regeneration at Service for DPF clogging is needed. Finally, a reduced DPF substitution for DPF over-clogging is obtained.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. 

1. A method for regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system, said Diesel engine system comprising an engine having an intake and an exhaust line and configured to inject quantities of fuel into a combustion chamber for raising a temperature of an engine exhaust gas, the engine comprising in said exhaust line the Diesel Particulate Filter (DPF), the method comprising: identifying a faulty condition of the Diesel engine system if the faulty condition is not critical; measuring an intake air charge to determine if the intake air charge is acceptable; and performing a regeneration process for said Diesel Particulate Filter (DPF).
 2. The method according to claim 1, wherein measuring the intake air charge comprises measuring an intake air flow rate and an intake air pressure in order to determine if the the intake air flow rate and the intake air pressure are within an acceptable range for initiating said regeneration process.
 3. The method according to claim 2, wherein said acceptable range is determined as a function of engine working point.
 4. The method according to claim 1, wherein said regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to a temperature set-point and duration of a conventional DPF regeneration process.
 5. An internal combustion engine, comprising: a first sensor adapted to sense a faulty condition of an engine system; a second sensor adapted to sense an intake air charge; and an electronic control unit that is adapted to receive the faulty condition and the intake air charge, the electronic control unit further adapted to: identifying the faulty condition of the engine system if the faulty condition is not critical; measure the intake air charge to determine if the intake air charge is acceptable; and initiate a regeneration process for a Diesel Particulate Filter (DPF).
 6. The internal combustion engine according to claim 5, wherein the internal combustion engine is a Diesel engine.
 7. The internal combustion engine according to claim 5, wherein the electronic control unit is further adapted to measure the intake air charge by measuring an intake air flow rate and an intake air pressure in order to determine if the the intake air flow rate and the intake air pressure are within an acceptable range for initiating said regeneration process.
 8. The internal combustion engine according to claim 7, wherein said acceptable range is determined as a function of engine working point.
 9. The internal combustion engine according to claim 5, wherein said regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to a temperature set-point and duration of a conventional DPF regeneration process.
 10. A computer readable medium embodying a computer program product, said computer program product comprising: a program for regeneration of a Diesel Particulate Filter (DPF) in a Diesel engine system, said Diesel engine system comprising an engine having an intake and an exhaust line and configured to inject quantities of fuel into a combustion chamber for raising a temperature of an engine exhaust gas, the engine comprising in said exhaust line the Diesel Particulate Filter (DPF), the program configured to: identify a faulty condition of an engine system if the faulty condition is not critical; measure an intake air charge to determine if the intake air charge is acceptable; and initiate a regeneration process for said Diesel Particulate Filter (DPF).
 11. The computer readable medium according to claim 10, wherein the program is further configured to measure the intake air charge by measuring an intake air flow rate and an intake air pressure in order to determine if the the intake air flow rate and the intake air pressure are within an acceptable range for initiating said regeneration process.
 12. The computer readable medium according to claim 11, wherein said acceptable range is determined as a function of engine working point.
 13. The computer readable medium according to claim 10, wherein said regeneration process is performed using a lower temperature set-point and employing a longer process duration with respect to a temperature set-point and duration of a conventional DPF regeneration process. 